Design and qualification testing of an automatic, closed-loop control system for implanted rotary blood pumps is proposed The control system is expected to significantly improve the efficacy and safety of treating Congestive Heart Failure patients with rotary blood pumps by eliminating problems associated with rotary pumps such as ventricular collapse caused by over-pumping and inadequate perfusion caused by under-pumping Three sonomicrometry transducers are permanently implanted within the wall of the left ventricle A software-based controller uses the sensed inter-transducer distances to optimally control the speed of a rotary pump to avoid excessive distension or contraction of the ventricle Specific aims of the project are to 1) Design and evaluate a clinical sonomicrometry lead suitable for human use -A formal specification will be prepared, leads and installation tools will be designed, prototypes will be fabricated, and in vitro and in vivo tests will be performed 2) Design and evaluate transducer interface circuitry capable of being sufficiently miniaturized for human implant - A formal specification will be prepared, circuitry will be designed, prototypes will be fabricated, and in vitro and in vivo tests will be performed 3) Develop and evaluate a closed loop pump control algorithm - A formal specification will be prepared, the algorithm will be developed, the algorithm will be evaluated using a computer model of the human circulatory system, and in vitro and in vivo tests will be performed 4) Fabricate and qualify sonomicrometry leads for human use - Production procedures will be prepared, a pilot production line will be setup, production processes will be validated, leads will be fabricated, and in vitro and in vivo qualification tests will be performed .